Piezo elements are used, inter alia, for positioning elements, ultrasonic transducers, sensors and in inkjet printers. The function of a piezo element is based on the deformation of piezoceramic materials such as, for example, lead-zirconate-titanate, under the action of an electrical field. If an electrical voltage is applied to the piezo element, it expands in the perpendicular direction with respect to the electrical field which is generated (inverse piezo effect).
DE 198 02 302 A1 discloses a multi-layer actuator structure. Such a multilayer actuator is composed of piezoceramic layers and internal electrodes for generating the electrical field. Since a plurality of the piezoceramic layers and internal electrodes are stacked one on top of the other, such an actuator is also referred to as a stack.
The internal electrodes make contact with two external electrodes which are applied to the outer side of the piezo stack, wherein the internal electrodes alternately make contact with just one of the two external electrodes. To make this possible, the internal electrodes are not made to extend as far as the outer side of the piezo stack in the regions in which said internal electrodes are not intended to make contact with the relevant external electrode. These regions are referred to as inactive zones since, when a voltage is applied to the external electrodes, the piezoelectric layers in the inactive zones are not completely penetrated by the electrical field of the internal electrodes and therefore also do not expand or do not expand very much compared to the remaining regions of the piezo stack. This brings about mechanical stresses within the piezo stack, and these damage the piezo stack.